Multiple wireless communication protocols may often simultaneously operate within the same radiofrequency band. For example, a variety of wireless communication protocols operate in the industrial, scientific, and medical (ISM) band defined by the ITU-R in 5.138, 5.150, and 5.280 of the radio regulations. These wireless communication protocols operating in the ISM band include band converted variations of the digital enhanced cordless telecommunications (DECT) protocol, IEEE 802.11 (also referred to herein simply as “802.11”), and Bluetooth. Where multiple wireless communication protocols are simultaneously in operation in a given region, interference across networks can undesirably affect performance of one or more systems.
For example, a DECT system monitors channels using a least-interfered-channel/listen-before-talk algorithm to select a channel and timeslot to use, and a move-on-error algorithm to change channels when corruption is observed on a link already set up. Unfortunately, for the case of sharing spectrum between a DECT-protocol-derivative product and an 802.11-protocol service, DECT's least-interfered channel algorithm does not detect 802.11-protocol usage of 802.11 channels efficiently.
FIG. 1 illustrates the detection method which DECT-derived products use to validate that a channel is free to use prior to starting transmissions on that channel. The DECT-derived system checks the candidate channel list periodically, looking at the signal level during one DECT timeslot, from time to time, to see if that timeslot is unused on that channel. The prior art DECT scanning system utilizes a round-robin scanning algorithm. The scanning algorithm tests twenty-four timeselots in one DECT TDMA frame on channel N, N+1, N+2 . . . N+M−3, N+M−2, N+M−1. The scan for other user activity repeats for M total channels. If the interference source is continuous, or if it repeats at 10 mS intervals, the testing will catch the usage of the channel by the other user. 802.11 usage, though, may be at other rates; commonly the 802.11 access points transmit a beacon every 100 mS, but data may be present or not at any time on the channel. The test of channel N may miss IEEE 802.11 activity on channel N in the round-robin period scanning algorithm.
In one prior art solution, an IT manager using a central management tool configures the DECT system by assigning certain channels for use. The IEEE 802.11 system is separately configured to use channels from its own selectable channel list which would not overlap with the selected DECT channels in use. While this approach addresses some of the technical issues, it requires action by the IT manager and does not result in an individual DECT unit being optimally configured for the environment in its physical proximity.
Thus, improved systems and methods for services in a shared frequency band provided by different protocols are needed.